Former Virginia Gov. Tim KaineTim KaineGOP lawmakers defend Trump military rules of engagement Trump supporters call for Kaine's son and other protesters to be prosecuted Senators demand Pentagon action after nude photo scandal MORE (D) kept up his torrid fundraising pace by raising $2.2 million since Jan. 1, his campaign announced Tuesday morning.

Kaine now has $4.4 million cash on hand for his Senate race, according to the campaign, a substantial war chest for a non-incumbent candidate at this point. That means he spent nearly half of what he raised in the last quarter, $1.1 million, since his cash on hand at the end of the year was $3.3 million.

Former Sen. George Allen (R-Va.), his likely opponent, has not yet announced his fundraising numbers. Allen had $2 million cash on hand as of the beginning of the year.

Kaine's strong fundraising likely stems in part from the network he built as head of the Democratic National Committee. Allen has also had strong fundraising quarters — he raised $1.1 million last quarter — but has been spending heavily, and netted only $200,000 last quarter.

The race is likely to be one of the most expensive in the country — outside groups on both sides have already been spending heavily on ads, and both Kaine and Allen now have super-PACs raising money to help their campaigns.